1. Field of the Invention
The present invention relates generally to writing instruments and, more specifically, to a writing instrument having a writing component containing volatile writing constituents, such as a marker, a water-based ink pen, a water-based ball point pen, a correction pen and a highlighter pen. The present invention also relates to a writing instrument in which a writing tip of the writing component can be maintained in an airtight condition when it is not used.
2. Background Information
In conventional writing instruments, such as a marker, a writing tip is maintained in an airtight condition so that it will not be dried when it is not used. Usually, in the case of a cap-type writing instrument, a cap is detachably attached to the front end of a barrel housing a writing component, and an airtight chamber surrounding the writing tip is formed by attaching the cap. In some cases, a soft material such as a rubber piece is provided in the cap so that it will abut on the writing tip. Further, in a case of a capless-type writing instrument, an airtight structure has been known wherein an airtight chamber surrounding the writing tip is disposed at the front portion of a barrel, in which the front end opening portion of the airtight chamber is opened and closed by a biasing member such as a spring so that the airtight chamber is opened when a writing component (e.g., a refill) advances and the airtight chamber is closed when the writing component retracts.
However, use of the conventional cap-type writing instrument requires the cumbersome step of removing the cap prior to a writing operation. In the case of the conventional capless-type writing instrument, since a spring is needed to open and close the opening portion, the number of parts becomes large, the manufacture and assembly thereof is complicated and expensive, and the resulting writing instrument tends to have a large diameter.
Moreover, conventional writing instruments having an airtight structure for the writing component are available. One such writing instrument has a rotating cam-type feeding mechanism disposed in a barrel for moving the writing component forward and backward. In general, such a rotating cam-type feeding mechanism is disposed in a rear portion of the barrel and has a rotational cam which abuts on a rear end of a writing component, a guide cam which allows the rotational cam to transfer in an axial direction, and an outer cam which is formed on an inner side of the barrel and guides the transfer of the rotational cam. However, the conventional rotating cam-type feeding mechanism is associated with a large number of parts and its manufacture and assembly is complicated. Furthermore, since a feeding mechanism is provided at the rear portion of the barrel, the entire length of the writing instrument tends to be long. Any attempt to form the conventional rotating cam-type feeding mechanism with a compact structure will require the use of an undesirable short writing component. Accordingly, if an airtight structure for maintaining the writing tip in an airtight manner is disposed at the front portion of the barrel, the entire length of the writing component is increased.